Technical Introduction
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EME
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Following block diagram gives an overview of a typical inverter test setup from the point of view of a single device under test (DUT):
The central item in the picture is the inverter, the device under test (DUT), which is electrically connected to:
Power supplies, communication interfaces, miscellaneous sensors
The HV battery
the electrical motor via typically 3 motor phases
and its position sensor
For inverters for power ranges of several kilowatts water cooling is usually applied.
The yellow marked parts are covered by the IRS EME active motor load:
synchronous motor
position sensor
and partially the HV battery in combination with a standard DC power supply.
To simulate the motor, there are generally different approaches commonly used:
Simulation of a simple passive load
Operation of a real motor, mechanically coupled with another motor-inverter-combination
High-end motor simulators
The following table shows the advantages and disadvantages of these setups:
✅ Very cost-efficient
⛔️ Very high price
⛔️ Very high price
✅ Small setup
⛔️ Space consuming setup
⛔️ Space consuming setup
✅ Full phase current
✅ Full phase current
✅ Full phase current
⛔️ Only reactive phase current
✅ Simulation of real phase currents
✅ Simulation of real phase currents
⛔️ No recuperation
✅ Recuperation possible
✅ Recuperation possible
🔶 Low DC currents
🔶 Real DC current from battery
🔶 Real DC current from battery
IRS EME active motor load is a solution which combines advantages of full-size high end motor simulators with the advantages of the passive coil, by keeping the concept simple, reliable and at a low cost.
🔶 Cost efficient
✅ Small setup
✅ Full phase current
✅ Simulation of real phase currents
✅ Recuperation possible
✅ Real DC current, but low power
To simulate a real load condition the induced voltage of the electrical motor needs to be generated, according to the equivalent circuit of a motor:
Voltage sources for high power are often also switched power supplies, while a good energy feedback is necessary to achieve a compact and cost-efficient setup.
Following picture shows the basic setup of the IRS electrical motor emulator for a three-phase-inverter as device under test (DUT):
The concept is based on the idea to directly couple two inverters and run against each other - both three phases and the DC-Link are directly coupled. As battery simulator a standard power supply may be used. With appropriate control of the motor simulator, the phase current flows from DUT to simulator via the phase coils and back to the DUT via the DC-Link, and vice versa.
Thus, the DC-Link of the DUT is stressed with a realistic current, but since the energy is flowing between the two inverters, the battery simulation needs only to provide the energy for the losses of the entire system. This is one of the most important benefits: a relatively small power supply without energy feedback to the grid can be used. With a power supply of only 20kW,
250kW can be simulated at 500V DC voltage,
350kW can be simulated at 850V DC.
The standard emulator variant is capable of handling voltages up to 1000V, resulting in even higher power ranges which can be simulated. In most setups, three basic setpoints define the operation:
EME generates the induced voltage of the motor
DUT is in current control mode, defining the applied torque to the motor.
EME defines the speed via the position sensor signal
In this document, we mostly refer to the voltage range up to 1000V, since this is covered by the standard IRS EME. In the meantime, different downsized variants are available which will be illustrated in later chapters. But the basic principle is the same for all IRS EME variants.
